AS-BUILT – WHAT DOES IT MEAN?

“As-built” – anyone involved in architecture and the construction industry will sooner or later come across this term. It is almost always linked with documentation. But what does as-built documentation actually comprise? How is it created and what is it needed for? There is no legal or regularitory definition of the term. Even within the industry, there may be different opinions when it comes to the definition and scope of a as-built documentation. Despite this, or rather precisely because of this, we will try to clarify all the questions surrounding as-built documentation in this article.

As-built documentation vs. construction drawing - what is the difference?

As-built documentation is documentation of the actual state of a building or construction project. A construction drawing, on the other hand, shows the planned state of a project. Anyone who has already been involved in a construction project knows that there can be considerable differences between the planning and the result. In order to obtain realistic documentation of the project, it is necessary to carry out as-built documentation in addition to the construction drawing.

Starting as early as possible: Documentation of construction progress

So does it make sense to simply create as-built documentation after the project is finished? Of course, the finished project should be fully documented. However, it is even better to start much earlier. Especially with larger projects, it is advisable to document the various stages of the construction progress. There are several reasons for this. On the one hand, it allows all those involved to be kept up to date on the progress of construction.

Even more important, however, is the comparison with the construction drawing and the planning. This way, possible complications can be recognized at an early stage and dealt with accordingly. After each construction step, costs can be adjusted if necessary, new permits can be obtained, materials can be exchanged, the statics can be recalculated, and so on. This makes it easier to avoid unpleasant surprises and cost explosions.

Of course, final as-built documentation should also be carried out after the project has been completed, and it is also worthwhile to acquire it for already existing structures. On the basis of the as-built documentation, subsequent conversion measures or installations can be planned and carried out. In addition, it provides important information for disaster control and rescue forces in case of an emergency.

How is as-built documentation created?

The purpose of as-built documentation is therefore clear. The question that arises next is how it should be carried out and what exactly it should contain. Regardless of whether the construction progress is to be documented or a project that has already been completed, the first thing to do is to create a accurate reality capture. Nowadays, depending on the size of the project, this is done by means of laser scanning and/or drone flights. If you work with a laser scanner, it generates a point cloud that must first be processed and evaluated with special software. Point clouds can also be generated from drone flights with special software such as Pix4D. With our Origins software for example, sections, floor plans and much more can be quickly created from the point cloud data. Data processed in this manner can then be imported into the CAD system, where a model of the project is created.

But a reality capture and a simple 3D model are often not sufficient for as-built documentation. Depending on the requirements, further information must be included in the documentation and there is also a lot to consider when creating the 3D model.

For instance, the level of detail, or LOD for short, plays an important role in 3D modelling. For example, should the valves of water systems be modelled down to the smallest detail or is it sufficient to roughly represent them in the correct position and orientation? Such questions should already be clarified and discussed with the modeller before the documentation is created. The modeller can determine in a personal conversation which LOD level is required for your project. There is no industry standard for the accuracy of as-built documentation. This is not least due to the fact that a higher degree of accuracy is associated with additional costs, which of course one does not want to bear if it is not needed for the project in question.

Another point that must be taken into account is additional information. For example, should the material of the floor, doors, windows, etc. also be documented? Which window model is used? Should invoices and static certificates be stored? These questions must also be clarified and the scope must be determined before preparing as-built documentation.

Ultimately, the scope and accuracy of as-built documentation always depends on your individual requirements. In general, however, it can be said that at least a rough digital reality capture by means of laser scanning is always useful.This way, errors can be avoided in the construction phase and possible subsequent construction work can be implemented more easily.

Do you have any further questions about as-built documentation or point cloud evaluation? Then write to us or call us under: +4971539295930.

Our support team will be happy to advise you!

WHAT ARE POINT CLOUDS?

Here’s an easy-to-understand introduction to the topic of point clouds. We answer the following questions:

Basics: What is a point cloud and how is it created?
What are point clouds used for?
How to work with point clouds?

Basics: What is a point cloud and how is it created?

A point cloud can best be explained with the help of a gadget that reached the peak of its popularity in the 00s and is now primarily used for presentations: the laser pointer. The laser pointer can be used to illuminate a precise point in a straight line. If you know exactly where the laser pointer is located in the room, you can also exactly locate the point that is being illuminated. After all, the laser beam is straight as a die and thus makes it possible to calculate the exact position of the point in space in relation to the origin (the laser pointer). Geodetic points in surveying are also measured according to this basic principle, only it’s a little more complex. Instead of a laser pointer, special tachymeters are used for this purpose.

And what does this have to do with point clouds? Quite simple. In addition to total stations, laser scanners have been used more and more frequently for surveying in recent years. These also work in the same way as our laser pointer, except that they can measure thousands or even millions of points simultaneously. Taken together, all the measured points constitue the point cloud.

What are point clouds used for?

Point clouds contain an incredible amount of information because every single point in the point cloud has its own X, Y, and Z coordinates. If we scan a staircase with a laser scanner, for example, we can use the resulting point cloud to determine exactly how straight the individual steps are, where the steps are worn and how high the deviation from the construction standard is. Accordingly, laser scanners and the point clouds they produce are always used when you want to document existing structures precisely, for example to digitise, measure or modify them.

For the design and optimization of production parts, for example in the automotive industry, very high-resolution hand-held scanners are usually used. They can capture even the smallest details and deviations. This allows a digital twin to be created on the PC. With the help of the twin, new prototypes can then be created and improvements digitally simulated and tested.

In the construction industry and as-built documentation of buildings, various scanners are used. Depending on the object, mostly terrestrial or mobile laser scanners, sometimes even drones. They are used to scan buildings for a variety of reasons, e.g. to plan an extension or renovation, to optimally position new equipment in production buildings, or to document the construction progress of various building projects.

These are just a few examples of applications. Point clouds are used wherever objects need to be precisely captured and digitized. Depending on the area of application, different laser scanners are used. They can produce different accuracies and point cloud sizes.

How to work with point clouds?

How to work with point clouds depends above all on what goal you are pursuing. As already mentioned, different laser scanners are used for different areas of application. The same applies to the software used to evaluate the point clouds. Our software solution, Origins (Pro), for example, is mainly used when existing buildings or landscape structures are to be digitally captured.

Regardless of which hardware and software solutions are used, there is an important step between the acquisition and the evaluation of the point cloud data: the registration.

Point Cloud Registration

During registration, individual scans or individual “sections” that were captured with the laser scanner are merged into a point cloud. If you want to register a complete building, for example, you often set up the laser scanner in the different rooms and scan them. Of course, in the end, you don’t only want to have individual scans of the different rooms. You prefer simply one large point cloud in which all the scans are available and linked together. To achieve this, you have to register the scans.

Behind the registration usually stands a rather complicated mathematical process. The accuracy of the data produced by the registration depends on how well the laser scanner captured the environment on site and how reliable the registration software used is. Fortunately, this process has become easier and easier in recent years. If you use a mobile laser scanner, for example, you often no longer have to make individual scans. You can simply walk through or around the object with the scanner. With this type of scanner, registration is also usually fully automatic and provided together with the hardware. The user does not need much know-how. The disadvantage here, however, is that mobile laser scanners are currently often not able to deliver as precise results as terrestrial laser scanners, i.e. scanners that are set up stationary and take individual scans one after the other.

There are different methods to register a point cloud. The best known are cloud-to-cloud registration, target-based registration, or plane-to-plane registration. Which method to use depends on many different factors, e.g. the laser scanner used, the desired accuracy, or your own preferences. Especially for newcomers, it is, therefore, advisable to have the scanning and registration carried out by experts. They not only register the point cloud but also “clean” it in most cases during the registration process. This means, for example, that duplicate scans or “noisy” areas of the point cloud are removed or the point cloud is professionally “thinned out” to reduce the file size.

Importing, processing, and passing on point cloud data

If you receive registered point cloud data, there is usually one more stumbling block to overcome before you can take measurements and create digital 3D models from the data – importing the data.

There is not just one file format for point clouds. In general, each laser scanner works with its own file format. Different software for processing are often using their own formats as well. As a result, there is hardly any software that can import all native file formats from the different laser scanners and processing software. We are very proud that our Origins (Pro) software can read and import over 25 different point cloud formats and export over 20 different formats (point cloud formats and others). However, even though we provide one of the greatest diversities on the market, it still doesn’t represent all native data formats. So what is the best way to deal with the different file formats?

Open exchange formats such as .las, .laz, .e57 or .xyz offer a solution to this problem. These file formats were developed by independent parties to solve the problem of data transfers. The .e57 format in particular has virtually become the industry standard. Almost all registration software of the laser scanner manufacturers can output the format and processing software for point clouds can also read the format. Therefore, in most cases, the surveyor will hand over the point cloud in .e57 format.

The disadvantage here is that the .e57 format, in contrast to the native formats, is less well compressed. Therefore it requires more storage capacity in comparison. However, the large amounts of data are normally no problem for point cloud software. After all, they were developed specifically for the processing and evaluation of point clouds. They can be used to carry out measurements and other evaluations. With Origins (Pro), for example, you can also create automatic floor plans that can be vectorized and much more.

However, if you want to create a 3D model from the point cloud, you need to employ a BIM or CAD software. These were not originally developed to handle point cloud data. Accordingly, many of these software still have major problems processing the data. Some CAD software, such as Autodesk Revit or AutoCAD, cannot read .e57 or other common point cloud formats. In order to use these software, the data must be converted again into the Autodesk formats .rcp or .rcs. Other CAD software cannot read point cloud data at all or can only import small amounts of data at once, which means that the point cloud has to be “split” again and imported in parts. These are all very tedious and time-consuming tasks.

To avoid this effort, the data is often first pre-processed in a point cloud software and then further processed in the CAD software. For example, Origins (Pro) can be used to create floor plans and vector lines, which can then be transferred to the CAD software in the correct position and with all the important 3D information in .dfx or .dwg format. These formats can be processed by almost any CAD software and require much less storage capacity than the entire point cloud. Of course, there are now also plugins for the most common CAD software that can transfer the 3D information from the point cloud software directly to the CAD software.

In conclusion, it can be seen that the acquisition and processing of point clouds, right up to the creation of a 3D model, still requires a great deal of expertise and know-how. Especially the amount of data and the data exchange between the different systems is still a challenge. Fortunately, a lot has already been done in recent years to simplify this process, also known as scan-to-BIM. We are also working every day to be able to import more data formats into our software and to simplify the handling so that even beginners can work with point clouds.

Do you have any further questions about point clouds or would you like to test our software yourself? Feel free to send us an e-mail to: support@pointcab-software.com. We would be happy to advise you in a personal meeting without obligation.

3D laser scanning 3D measurement point clouds